Dimensional Weight (Dim Weight): What It Is and How It Affects Shipping Prices

As anyone in ecommerce can tell you, shipping products to customers is a major component of daily operations. On the surface, boxing up and shipping products looks like it should be a simple process, but looks can be deceiving. We’ve already helped to demystify the concept of shipping zones. Now let’s turn our attention toward dimensional weight— DIM weight for short—a term that can cause confusion to those new to shipping.

Shipping prices are generally based on the weight of the package being shipped. As an example, let’s assume that sending a 1 pound package from New York to Chicago costs around $8.00, while shipping a similarly-sized 5 pound package costs $12.00. As expected, the heavier package costs more to ship. But this will not always be the case.

The reason for this is that shipping carriers also take into consideration the size, or dimensions, of the package when determining the shipping price. After all, a big package takes up space that could have been used for several smaller packages, regardless of weight.

Dimensional Weight Defined

Dimensional weight, also called volumetric weight, is a pricing technique for commercial freight transport (including courier and postal services), which uses an estimated weight that is calculated from the length, width, and height of a package. To determine the dimensional weight, one must multiply the package’s length x width x height (L x W x H). The result of this calculation is then divided by a special number called the DIM factor, which represents cubic inches per pound and is related to the package’s density. Common DIM factors include 139 and 166, but shipping carriers use other ones as well.

For example, assume a package has a length of 12 inches, a width of 10 inches, and a height of 7 inches. The shipping carrier has provided a DIM factor of 139. To calculate DIM weight, use the following formula: (12 x 10 x 7) / 139, as follows:

Actual Weight or DIM Weight?

Let’s think back to our first example: a 1-pound package being shipped from New York to Chicago. We said that would cost about $8.00. Well, if the package size is 12” x 10” x 7” with a DIM factor of 139, as in the example above, it would cost significantly more. That’s because the shipping carrier would use the DIM weight instead of the actual weight.

When determining shipping price, the higher of the DIM Weight or actual weight is used. Thus, in our example, a weight of 6.04 pounds would be used instead of 1 pound. Also, take note that many shipping carriers round weights up to the nearest pound, so it is likely you would be charged a rate based on a 7-pound package for this shipment. In our hypothetical example, this brings our shipping price up from $8.00 to about $18.00. A hefty difference!

Other Considerations

The above examples all assume the use of the United States Customary System of measurements. If you’re using the metric system, your units will be centimeters and kilograms and the DIM factor will change accordingly (a DIM factor of 5000 cubic centimeters per kilogram is commonly used).

Many shipping carriers ask you to round your measurements to the nearest whole number. So, if your package has a length of 5.75”, round up to 6”. If the package length is 5.45”, round down to 5”.

Important Takeaways

Here are the most important points to remember about DIM Weight:

Dimensional (DIM) weight is also called Volumetric Weight

It’s a pricing technique used to determine the cost of shipping based on a package’s size and density

It’s calculated as follows: (L x W x H) / DIM Factor = DIM weight

The DIM factor is determined by the shipping carrier. It is often 139 or 166, or 5000 if the metric system is being used

The greater of actual weight or dimensional weight is used to determine the shipping price

Dimensional weight can have a huge impact on the cost of shipping. With that in mind, always pack your items efficiently, using the smallest shipping carton you can while still keeping the products safe and secure.